Re: [PATCH v2] scsi_debug: fix sleep in invalid context

[Douglas Gilbert <dgilbert@interlog.com>]

On 2016-06-07 09:55 PM, Christoph Hellwig wrote:
>> +static int p_fill_from_dev_buffer(struct scsi_cmnd *scp, const void *arr,
>> +				  int arr_len, unsigned int off_dst)
>> +{
>> +	int act_len, n;
>> +	struct scsi_data_buffer *sdb = scsi_in(scp);
>> +	off_t skip = off_dst;
>
> Why off_t which is a signed value instead of the unsigned in passed in?

Because off_t is the type of the last argument to sg_pcopy_from_buffer()
which is where the off_dst value goes. So there is potentially a size
of integer change plus signedness, IMO best expressed by defining a
new auto variable. I notice some projects have a uoff_t typedef for
offsets that make no sense when negative (like this case), but not the
Linux kernel.

>> +#define RL_BUCKET_ELEMS 8
>> +
>>   /* Even though each pseudo target has a REPORT LUNS "well known logical unit"
>>    * (W-LUN), the normal Linux scanning logic does not associate it with a
>>    * device (e.g. /dev/sg7). The following magic will make that association:
>> @@ -3285,12 +3315,14 @@ static int resp_report_luns(struct scsi_cmnd *scp,
>>   	unsigned char select_report;
>>   	u64 lun;
>>   	struct scsi_lun *lun_p;
>> -	u8 *arr;
>> +	u8 arr[RL_BUCKET_ELEMS * sizeof(struct scsi_lun)];
>
> just use an on-stack array of type struct scsi_lun here, e.g.:
>
> 	struct scsi_lun arr[RL_BUCKET_ELEMS];
>
> Which you can then use directly instead of lun_p later, but which can
> also be passed p_fill_from_dev_buffer as that takes a void pointer.

Can do.

Doug Gilbert